Southern Illinois University School of Medicine, Springfield, IL, Distinguished Scholar and Professor of Pharmacology, 2004-2012

Research Interest and Specialties:

Recent Research Activities in the Caspary Auditory Neurobiology Laboratory

Aging: Age-related hearing loss impacts 30-50% of individuals over 65 years of age. An age-related loss of speech understanding causes many elderly, cognitively intact, individuals to withdraw from active participation in society. Our recent studies focused on the nature of inhibitory receptors and how they influence processing of acoustic information in the auditory thalamus (MGB). We specifically characterized role of extrasynaptic GABAA receptors in the auditory thalamus. We described the properties of the tonic currents mediated by these receptors using molecular neurochemistry and slice recordings from adult and aged animals. These studies describe a profound (50%0 age-related loss in the number and function of extrasynaptic GABAA receptors in auditory thalamus.

Tinnitus: Aside from studies on the impact of aging the Auditory Neurobiology Laboratory examines animal models of tinnitus. This “ringing in the ears” affects 10% of the general population and an overwhelming number of military personnel. In a parallel series of studies on extrasynaptic GABAA receptors in animals with tinnitus, we found an increase in the sensitivity of these receptors. These tinnitus results, support the thalamocortical dysrhythmia hypothesis underpinning tinnitus pathology at the level of thalamus. Recordings from awake rat auditory thalamus showed increased spontaneous activity and increased sound-evoked activity in neurons in MGB of animals with tinnitus. Many tinnitus-related response changes correlated directly with the tinnitus score of the individual animal. Animals showing more tinnitus, showed more bursting and more spontaneous activity, etc.

Role of Cholinergic Receptors in Aging and Tinnitus: Recent work has focused on cholinergic inputs to the auditory thalamus. When a signal is difficult to detect or unusual, brainstem cholinergic neurons are activated by descending pathways from the auditory cortex and the hippocampus. The present studies attempt to identify the location and age-related changes of nicotinic cholinergic receptors in the auditory thalamus.

Animal Models of Auditory Processing: Understanding the role of bottom-up and top-down processing of acoustic information is critical to understanding age-related loss of speech understanding. Collectively these studies of plasticity in models of tinnitus and aging will both in vitro and in vivo electrophysiologic methods with a range of molecular neurochemical and imaging techniques to address these important neuroscience questions.